An air turbo rocket (ATR) is an air breathing propulsion system that uses fuel gases produced by a gas generator propellant to operate the engine's turbine. The turbine expands these hot gases and provides energy to the compressor. The compressor then compresses the air from the air inlet and the air flows from the compressor to the combustion chamber. The fuel gases flow from the turbine to the combustion chamber where they react with the compressed air. The combustion gases from the combustion chamber are expanded through a nozzle that produces the rocket's thrust.
A turbojet is an air breathing propulsion system that uses the gases produced in the combustion chamber to operate the engine's turbine. The turbine expands the gases produced in the combustion chamber and provides energy to the compressor. The compressor then compresses the air and the air flows to the combustion chamber. Fuel is injected into the combustion chamber where it reacts with the compressed air. The combustion gases go through the turbine and to a nozzle where the gases are expanded to provide thrust for the rocket.
The ATR has several advantages over the turbojet propulsion system. Since there is no turbomachinery located downstream of the combustion chamber, the ATR can operate at higher combustion temperatures. The ATR can operate at higher speeds because the turbine temperature is independent of air inlet conditions. At subsonic conditions, where the air is not compressed much because of the lower rocket velocity, the ATR operates with better performance since the energy supplied by the turbine is independent of air inlet conditions.
The use of an ATR in a tactical weapon system has not been considered because of limitations in present gas generator formulations. The ATR has not been able to compete with the turbojet propulsion system because the turbojet uses a liquid fuel, JP-10, which has a gravimetric heating value (GHV) of approximately 18,000 btu/lb whereas gas generator propellants for the ATR have GHVs between 5,000 to 9,000 btu/lb.
The object of this invention is to provide a gas generator formulation that can provide enough energy for an ATR turbine but also have a GHV of 18,600 btu/lb.
Another object of this invention is to provide a gas generator formulation that can be used with other airbreathing propulsion systems that require fuel gases with a high GHV.
Further exploitation of this invention is the use of a gas generator propellant formulation in a pulse detonation engine (PDE). A PDE is essentially a shock tube into which both a fuel gas and air is introduced before an ignition device detonates the explosive mixture of gases. The PDE engine is throttled by varying the gaseous flow rates. This engine has a significant weight advantage over the ATR or turbojet because is has no turbomachinery. This engine can also be made of lower cost materials that do not have the high temperature requirements of a turbojet turbine.
Therefore a further object of this invention is to provide a family of gas generators that can be used with airbreathing engines such as the ATR and PDE. The ATR goal is to provide enough energy for an ATR turbine but also have a GHV of 18,600 btu/lb. The PDE goal is to provide an effluent with a GHV of 18,600 btu/lb. but also have good detonation properties.